Selenicereus undatus is a fast-growing, hemi-epiphytic climbing cactus in the family Cactaceae, world-renowned for producing the white-fleshed dragon fruit or pitahaya/pitaya. While its precise native range is debated due to extensive historical cultivation, it is indigenous to the seasonally dry forests of Mexico and Central America. The genus name Selenicereus is derived from Selene, the Greek goddess of the moon, and cereus, meaning "candle," a reference to its nocturnal blooming habit; the species epithet undatus is Latin for "waved," describing the characteristic undulating or scalloped margins of its three-angled green stems. Historically, it was introduced to Southeast Asia by the French in the 19th century, where it became a major commercial crop, particularly in Vietnam.

The plant is characterized by its sprawling, vine-like stems that use aerial roots to cling to trees or rock faces. It produces some of the largest flowers in the cactus family—fragrant, white, nocturnal blooms that are typically pollinated by bats or large moths. The resulting fruit is oval, covered in bright pink or red leathery skin with prominent greenish "scales" or bracts. Selenicereus undatus is highly valued in xeriscaping and sustainable agriculture due to its high water-use efficiency and ability to thrive in tropical climates with distinct wet and dry seasons.

The fruit of Selenicereus undatus is prized for its refreshing, mildly sweet pulp and the pleasant "crunch" of its numerous tiny, black, edible seeds. The flavor is often described as a subtle cross between a kiwi and a pear. In modern gastronomy, it is a staple in smoothie bowls, tropical salads, and as a vibrant garnish for desserts and cocktails. In its native Latin America, the fruit is often used to make agua fresca, while in Asia, it is frequently consumed fresh as a palate cleanser. The flower buds are also edible and are sometimes cooked as a vegetable or used in soups in Chinese cuisine.

Nutritionally, dragon fruit is low in calories but rich in essential nutrients, including Vitamin C, iron, and magnesium. The seeds are a significant source of heart-healthy omega-3 and omega-6 fatty acids. The fruit contains a variety of bioactive compounds, most notably betacyanins (in the peel) that can change the color of urine and various phenolic acids that provide antioxidant and anti-inflammatory benefits. Unlike the red-fleshed varieties (S. costaricensis), the white pulp of S. undatus is lower in betalains but higher in certain flavonoids. Studies have also explored its prebiotic potential, as the many types of oligosaccharides (such as nystose) in the pulp can stimulate the growth of beneficial gut bacteria like Bifidobacteria and Lactobacilli.